Field of the Invention
The present invention relates to wireless communication and, more particularly, to a method and apparatus for performing link adaptation.
Related Art
A Machine-to-Machine (M2M) system has recently been in the spotlight as the next-generation communication technology. In the IEEE 802.11 WLAN, a new standard is being established in order to support M2M. An M2M system means a network over which a machine not a human being becomes the main body of communication and exchanges pieces of information. A temperature sensor, a humidity sensor, a camera, home appliances, such as TV, a process machine in a factory, or a large-sized machine, such as a vehicle, may become one of the elements of an M2M system. With the recent advent of various communication services, such as smart grid, e-Health, and ubiquitous, M2M technology is used a lot in order to support the various communication services. An M2M system has the following characteristics.
1) A very large number of STAs: M2M assumes a very large number of STAs unlike an existing network. This is because not only machines owned by persons, but also sensors installed in homes and companies must be taken into consideration. Accordingly, a very large number of STAs may be connected to one AP.
2) Low traffic load per STA: An M2M terminal has a traffic pattern in which surrounding information is collected and reported. Accordingly, information does not need to be frequently transmitted, and the amount of the information is small.
3) Uplink-oriented: M2M is chiefly configured to receive a command in downlink, take action, and then report resulting data in uplink. Thus, uplink becomes the center in M2M because major data is commonly transmitted in uplink.
4) Longer lifespan of an STA: An M2M terminal is chiefly operated by the battery, and a user may not frequently charge the M2M terminal Accordingly, it is necessary to guarantee a longer life span by minimizing the consumption of the battery.
5) Automatic recovery function: An M2M terminal needs an automatic recovery function because it is difficult for a person to directly manipulate the M2M terminal in a special situation.